Method and apparatus for producing mineral fibers



Nov. 28, 1961 w. P. WARTHEN METHOD AND APPARATUS FOR PRODUCING MINERAL FIBERS Filed Sept. ll, 1957 United States Patent METHOD AND APPARATUS FOR PRODUCING MINERAL FIBERS William P. Warthen, Newark, Ohio, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware Filed Sept. 11, 1957, Ser. No. 683,278 12 Claims. (Cl. 18-8) This invention relates to method and apparatus for producing mineral fibers or filaments of ribbon-like shape formed of heat-softenable mineral materials by attenuation.

Attempts have been made to fashion mineral materials into fiat fibers or filaments of noncircular cross-section but such endeavors have not been successful by reason of the inherent characteristic of molten mineral material such as glass in a plastic or flowable state to assume the configuration of circular cross-section. This condition obtains even though the molten mineral material is discharged or extruded through orifices of noncircular crosssection, the surface tension and molecular interadhesion being of sutficient magnitude to cause the material to immediately form a substantially circular cylindrical body or stream. By reason of this characteristic, fibers or filaments formed fromheat-softened mineral materials by attenuation have been of substantially circular crosssection.

Ribbon or film glass of a thickness of a few microns has been produced by methods involving the delivery of a tubular stream of softened glass between mechanically driven rolls which squeeze the tubular formation to a flat film, one method of this character being disclosed in the Slayter and Snow Patent 2,457,785 granted December 28, 1948. Another method involves flowing or drawing glass in the form of a thin walled cylinder which is broken into small flakes. Attempts have been made to produce a thin ribbon of glass through the use of drawing ro-l'ls but it hasbeen found that the glass stream tends to neck in to a fraction of its initial width and there is a tendency for the formation of a bead or ridge to .be formed along the edges due to surface tension, and such attempts have resulted in failure. As far as I am aware attempts to produce flat fibers or filaments by direct attenuation from a stream of molten mineral material have heretofore been unsuccessful.

The present invention embraces a method of successfully forming fibers, filaments or thin films of mineral material of noncircular cross-section by direct attenuation of a stream of the material.

An object of the invention embraces the provision of a method of forming fiat fibers, continuous filaments or film by establishing differential thermal conditions in different regions in a body of mineral material and attenuating material from the body.

An object of the invention resides in a method involving feeding heat-softened material to a partially confined zone to establish differential thermal conditions in the material with consequent variations in viscosity in difierent regions in the material and attenuating the material to form filaments, fibers or film of noncircular crosssection.

Another object of the invention is the provision of a method wherein molten filament or film-forming material is delivered to a Walled region having an open area and the material suspended in said region subjected to differential cooling enabling the attenuation of the material into a linear body of substantially rectangular cross-secn'on.

Another object of the invention is the provision of an apparatus for flowing fiber or film forming material from a supply to a generally cubically shaped region having 3,010,146 Patented Nov. 28, 1961 tantly with the attenuation operation whereby the metal coating is fixedly bonded to the fibers.

A further object of the invention resides in a method of forming mineral material into fiat fibers which may be twisted during attenuation to form a spirally shaped fiber.

Another object is the provision of a method and ap paratus for thermally controlling a body of fiber or filmforming material to establish thermal differentials in different regions of the body of material whereby the same may be drawn or attenuated into fiat fibers or film of substantially uniform thickness.

Still a further object of the invention is the provision of an apparatus adaptable for attenuating a body o-fhea-tsoftened material into a fiat continuous filament or fiber by winding the attenuated film or fiber upon a collet moving at highspeed whereby flat fibers of extreme fineness may be efficiently produced with inexpensive equipment.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is a semidiagrammatic view with certain parts shown in section illustrating a type of apparatus for forming flat fibers or film from heat-softened mineral material;

FIGURE 2 is a front elevational view ment shown in FIGURE 1;

FIGURE 3 is a view similar to FIGURE 1 illustrating a method of applying a coating or layer of metal or other of the arrangematerial to completely surround a fiat filament or fiber;

the form of an independent feeder receptacle adapted to FIGURE 4 is a fragmentary isometric view of a fiat fiber illustrating a coating of metal on one major face thereof;

FIGURE 5 is an isometric view illustrating a fiat fiber completely coated with metal or other material;

FIGURE 6 is a fragmentary view showing a flat fiber oriented in a spiral or twisted formation, and

FIGURE 7 is a semidiagrammatic view illustrating the method of forming comparatively thin film of heatsoftened material by attenuation.

The method and apparatus of the invention are especially adapted for producing flat or ribbon-like continuous filaments, fibers or film from heat-softenable minerals, such as glass, slag, or fusible rock. However, it is to be understood that the principles involved in the formation of flat filaments, fibers or film may be utilized for the production of linear bodies of other noncircular cross-sectional configurations through the establishment of thermal differentials in Various regions of a body or quantity of material from which the linear bodies are drawn or attenuated.

Referring to the drawings in detail, a form of apparatus is illustrated for carrying out the method of the invention which includes a receptacle, tank or feeder 10 containing a supply 12 of heat-softened glass or other' fiber or film-forming mineral material. The receptacle 10 may be a forehearth connected with a melting furnace in which glass batch is reduced to 'a molten state or in be heated by electrical energy in a conventional manner. When a heated feeder is utilized, the fiber or film-forining material is preferably delivered into the receptacle as preformed marbles or spheres which are reduced to molten or a flowable state by heat applied to the feeder.

The glass in the feeder or receptacle isdelivered to a partially confined zone configurated or shaped to set up thermal or temperature differentials to modify the viscosity of the material in dilferent regions thereof where-- by a linear body of noncircular' cross-section may be drawn from the material. Disposed beneath the floor 14 of the receptacle isa member or shield 16 which, in the embodiment illustrated is of three-sided configuration including a rear wall 18 and spaced side walls 20.

The walls or fins 18 and 20' define or establish a reservoir or chamber 22 of generally cubical shape as the walls 18 and 20 are substantially square. The Walls are welded as at 24 or otherwise securely joined to the bottom wall or floor 14 of the receptacle 10 as shown in FIGURES 1 and 2. An orifice or passage 26 is formed in the bottom wall v14 through which glass 12 or other mineral material from the receptacle flows into the chamber or partially confined zone '22. The glass in the receptacle is maintained at a temperature rendering the glass quite viscous although flowable.

In carrying on fiber or film-forming operations the operatonthrough the use of a suitable tool, diverts or deflects the heat-softened glass flowing through the orifice 26 into contact with the inner surfaces of the Walls 18 and 20 and the lower surface of bottom wall 14 of the receptacle to wet the walls so that the flowable glass will adhere to the Wall surfaces. This action floods the chamber 22 With the glass to form a body or quantity 28 of glass in the chamber which, during attenuating operations, assumes a configuration of the general contour as indicated in FIGURE 1.

The glass or material in the feederor receptacle 10 is maintained at a temperature whereby the viscosity of the glass in the chamber 22 is such that the glass is suspended from the walls. In the embodiment illustrated in FIGURES l, 2, 3 and 7, the rear wall 18 and the side walls 20 are substantially square and hence define a reservoir, chamber or region 22 which is substantially cubical in shape, the fourth side and bottom being open or unrestricted. 7

Through the provision of an open sided reservoir, the surface 30 of the body of glass 28 in the reservoir, is exposed to direct contact with the ambient air while the remaining surface regions of the body of glass 28 are in contact with the central region of the bottom wall 14 of the receptacle and the interior surfaces of the rear, and side walls 18 and 20 forming the shield. Direct contact of the surface region 30 of the body of glass 28 with the air chills or reduces the temperature of the glass at the region 30 at a faster rate than the regions of the glass in contact with the walls 18 and 20.

Hence thermal differentials are set up in different regions of the body of glass 28 establishing varying viscosities therein whereby the glass may be drawn or attenuated from the reservoir 22 into a linear body, filament, fiber or film of noncircular cross-section.

As illustrated in FIGURE 1, the glass or other fiber or film-forming material 28 is drawn or attenuated from the region at the lower terminus of the rear Wall 18 in forming a linear body, the rear wall 18 being of planar shape and the attenuated linear body or filament 32 of flat or rectangular cross-section as shown in FIGURE 4.

The fiber or filament 32 is attenuated by being wound around a collet 35 mounted upon a rotating arbor 36, the col-let being rotated at a desiredspeed by a motor (not shown) to secure a fiber or filament of desired size.

The principles involved in the method of successfully forming a linear body, filament or fiber of noncircular cross-section through the use of the apparatus disclosed are as follows: The body of glass 28 is of a viscous constituency so that it is supported and suspended by ad- .hesion to the walls of the shield 16. The exposed surface region 30 of the body of glass 28 is cooled and its temperature reduced by contact with the ambient air at a faster rate than those regions of the body in contact with the walls 18 and 20. V

' This cooling action substantially increases the viscosity of the glass at the surface region 30 and tends to re-, tard the necking in of the glass being drawn from the terminus of the rear wall 18 of the shield as the glass at the surface region 30 converging at the region indicated at 38 approaches a state of solidification. This condition provides substantial resistance to flow of the glass and is sufficient to prevent the natural or inherent tendency for glass to gravitate to a circular cross-section.

The glass in contact with the walls 18 and 20 is-at higher temperatures and hence lower visoosities and flows into convergence with the more viscous glass atthe region 38 from which the filament or body is drawn or attenuated. As shown in FIGURE 2, the glass is drawn from a transverse linear zone 38 provided by the terminus of the planar wall 18 and a'sthe glass leaves the wall 18 it is of rectangular cross-section and is solidified by further contact with air into a fiat linear body or filament 32. Several factors affect the erosssectional configuration, the Width and thickness of the attenuated body or filament. The viscosity of the body of glass in the reservoir 22 should be high enough to maintain a condition of con stant flooding in the region defined by the walls 18 and 20, as the space between the side walls 20' must be filled with softened glass and the walls 18 and 20 wetted by the glass in order to secure a flat filament or fiber. It is believed that the tendency for the glass'to wet over the surface of the wall 18 including the terminus region thereof from which the filament is drawn is an important factor in forming the flat filaments or fibers. The linear rate of attenuation in a large measure determines the.

width and thickness of the attenuated body. 7

As an operating example, an apparatus is employed wherein the walls 18 and 20 are each substantially /61" square and the passage or orifice 26 in the floor of the receptacle l d-is approximately in diameter. By attenuating the body, filament or fiber at the rate of upwards-of ten thousand linear feet per minute, a flat ribbonlike. continuous filament or fiber of a thickness of two or more microns and of awidth approximately eight to twelve times its thickness is formed.

- By varying the operatin factors abovementi oned, the thickness and width of the attenuated filament or fiber may be varied and controlled. Therelative'dimensions of the rear and side walls of the shroud l'fi, and the spacing between the side walls, may be varied to modify the width and thickness of the flat filament Furthermore, while the configuration of the shield 16 illustrated is particularly adapted to fort'nv flaflrihbon-like filaments o'Pfibetsthe major surfaces of which are in parallelism, it is to be understood that the shape of the walled shroud or shield 16 may be modified to produce attenuated linear bodies of other noncirc'ular crossse'ctional configurations. Variations in cross-sectional configuration may be obtained by varying the thermal The flat, ribbon-like fibers or filaments produced by the method and apparatus above described may; be surface coated with other materials, such as metals, metal flloys or other glasses.- FIGURE 1 illustrates an arrangement for. applying a coating of metal .topne face or surface; of a flat filament 32. Disposed adjacent the filament ,32"

is; a receptacle 40 adapted to contain a supply of molten metal 42; The receptacle 40 is formed with-a lip 44 which is positioned adjacent the: path of movement-of the flat filament 32.

The molten metal 42 flows from the supply in the receptacle onto the lip 44, the adjacent fiat surface of the fiber 32 engaging the molten metal on the lip 44 whereby during linear movement of the filament, one surface thereof is coated with the metal. The transfer of the molten metal onto the filament is effected by a wiping action enhanced by the inherent characteristic of glass to acquire a coating on a nascent surface.

Metals that have been found suitable for coating the filaments or fibers are aluminum, chromium, zinc, lead or the like. The winding collet 35 is spaced a distance sufiicient from the region of application of the coating to the filament so that the metal is completely set or solidified before the coated filament is wound onto the collet. FIGURE 4 illustrates a fiat fiber 32 with a metal coating 33 thereon. The metal coating is preferably applied to the filament at or just prior to the point of complete attenuation or solidification of the glass.

FIGURE 3 is illustrative of an arrangement similar to FIGURE 1 for completely coating a fiat filament or fiber with metal. In this arrangement, the receptacle 40' contains molten metal 42' which flows onto a lip 44 providing a quantity of the coating metal at 45. The filament 32 is pulled or drawn through the meniscus of metal 45 so that both major surfaces and the edge regions receive a coating 33 of the metal. In order to eifect a complete coating on the flat filament 32, the filament is drawn away from the terminus of the wall 18 in an angular direction as shown in FIGURE 3, to completely immerse the filament in the metal supported on the lip 44'. FIGURE 5 illustrates the fiat fiber of filament 32 completely embedded in or surrounded by the metal coating 33'.

The coated or uncoated flat continuous filament may be twisted prior to its collection upon a winding collet. The twisting of the flat filament or fiber may be accomplished by passing the filament through a rotating guide (not shown) having a transversely elongated opening in the axial region thereof to accommodate the flat filament.

By rotating the guide, the wall surfaces defining the elongated slot in the guide engage and twist the filament to the configuration shown at 32a in FIGURE 6. The amount of twist or spiral configuration imparted to the fiber or filament 32:: may be modified by varying the speed of rotation of the twisting guide or varying the ratio of speed of rotation of the winding collet 35 to that of the twisting means.

The arrangement of receptacle and the chamber 22 provided by the walls or fins 18 and 20 may be utilized to produce thin film glass of substantial width in the manner shown in FIGURE 7. In forming film glass, the glass of the body 28' contained in the reservoir or chamber 22 is preferably drawn in a substantially horizontal or lateral direction from the shield 16.

In forming film glass in the manner illustrated in FIG-, URE 7, both the surface regions of the body of glass 28' exposed to the ambient air through the open side and the open bottom region of the shield are chilled and the viscosity increased so that during attenuation of the film 48, the chilled regions are drawn into coextensive converging relation and by reason of the increased viscosity, the linear body or film does not neck in appreciably.

Thus, a glass film of a width only slightly less than the transverse dimension between the walls 20 is formed, the thickness and width of the film being determinedin a large measure by the initial viscosity of the glass 28' in the chamber 22, the extent of temperature reduction or chilling of the exposed regions of the body of glass 28' and the rate of linear attenuation of the film. The film may be attenuated by pull rolls or other suitable means.

The attenuated film 48 maybe coated with metal on one or both surfaces by feeding molten metal onto the film. The molten metal is preferably applied to the film before attenuation is complete in order to improve the adhesion between the molten metal and the glass.

While a single filament or fiber attenuating unit is illustrated, associated with the receptacle 10, it is to be understood that a substantial number of units 16 may be secured to a glass feeder or bushing associated with a forehearth of a glass melting furnace whereby a substantial number of flat filaments or fibers may be formed concomitantly.

The flat filaments or fibers are adaptable for many and varied uses. The uncoated fibers may be processed into filter'mats to obtain improved filtering efiiciency. For example, the flat filaments Or fibers may be oriented in a general pattern with their major surfaces facing in the same direction and in overlapping relation. This orientation causes a greater turbulence of the air or other gas passing through the filter in directions generally normal to the major surface of the filaments and enhances the removal of foreign matter. Flat filaments may be used for polarization or light channeling purposes.

The metal coated flat filaments or fibers are adaptable for many uses. 'For example, coated fibers may be used for decorative purposes. When coated on one side with metal, they are highly reflective and become miniature mirrors. The spiral fibers, both coated and uncoated are useful for decorative purposes. Metal coated fibers may be processed into mats having high insulating efiiciency. By orienting the metal coated surfaces of the fibers whereby they face generally in one direction in a mat, the coated surfaces, being heat reflective, provide refiective insulating properties in addition to the conventional insulating characteristics of a fibrous mat.

The method of the invention may be employed in forming laminated units suitable for electrostatic condensers.

For example, two flat filaments may be concomitantly formed, one of the filaments coated with metal on one face and the two fibers brought into engaging relation with the metal disposed between the fibers providing a glass and metal laminate. Metal coated filaments may be employed in producing electrostatic filters, high frequency signal reflection, or electromagnetic energy reflection and for current conducting purposes.

The. film glass formed by the method exemplified in FIGURE 7 may be coated with metals or other glass by feeding the coating materials to the softened glass within the region defined by the walls 18 and 20 or applied to the film at or in advance of the-zone of complete attenuation.

Curly filaments may be produced by feeding a coating glass having a different coefiicient of expansion onto the filaments in softened condition.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof. a

I claim: 7 i

'1'. The method of processing heat-softened mineral material including the steps of delivering heat-softened mineral material to a partially confined zone, subjecting an unconfined region of the material to air to establish differential temperatures in the mineral material at the confined zone to increase the viscosity of a portion of the material at said region, and drawing the material from the confined zone-into a filament of noncircular cross-section. I

2. The method of forming heat-softened mineral material into filaments of noncircular cross-section including 1 the steps of delivering heat-softened mineral material to suspending the material in said zone, cooling an unconfined region of the material at the a partially confined zone,

said zone to increase the viscosity of a portion of the material. at said region, and drawing the material from the confined zone into a filament of noncircular crosssection.

3. The method of processing heat-softened material including delivering heat-softened material into a walled 7 reservoir having a lateral open area, flooding the reservoir to wet the walls with the material, reducing the temperature of the material adjacent the lateral open area to increase the viscosity of the material adjacent the open area, and"'drawing a stream of the material from the reservoir at a 'zdrie of difierential viscosities into a flat filament.

4. The method of forming heat-softenable material into a filament of substantially rectangular cross-section including flowing a stream of the material into a partially shielded region, flooding the material over the shielded region to suspend the material therein, exposing a surface or the material in the shielded region to direct contact with air to increase the viscosity of the material adjacent the exposed surface, drawing material of difierential v iscosities from the shielded region to form the filament of noncircular c'r'oss'-section, and applying a coating of metal to the filament as the filament is being med- 5. The method of forming glass into a flat filament including establishing a supply of molten glass in a receptacle, flowing the glass through an orifice from the receptacle to a partially shielded region beneath the receptacle to establish a quantity of glass suspended in the region, reducing the temperature of aportion of the suspended glass to increase the viscosityof the portion, and attenuating the suspended glass in the shielded region from the Zone' of convergence of glass of difierent viscosities to form aflat filament.

6. The method of forming glass into a fiat filament including establishing a supply of molten glass in a receptacle, continuously flowing the glass through an orifice from the receptacle to a partially shielded region beneath the receptacle to establish a quantity of glass suspended front the receptacle, reducing the temperature of a portion of the suspended glass to increase the viscosity of the portion above that of the remaining glass in the shielded region, drawing the glass of different viscosities from the shielded region into a fiat filament, and coating the fiat filament with metal at the region of attenuation.

7. Apparatus for processing heat-softened material into filament form including, in combination, a receptacle adapted to contain heat-softened material, a shield associated with the receptacle, said'shield being shaped to' detitle a chamber adapted to receive material from the receptacle and having a lateral open region whereby a surface of the material in the chamber is exposed to increase the viscosity of the material adjacent the lateral open region of the chamber, and means for drawing the material from the chamber into a filament of noncircular cross-semen.

8. Apparatus for forming heat-softened mineral material into a filament including, in combinationa receptaele adapted to contain heat-softened mineral material, a shield secured to and disposed beneath the receptacle, said shield defining a chamber having an open' side and an open bottom region, means for delivering material from the supply into the; shield, said open side and bottom providing direct contact of ambient air with the ex posed regions of the material in the chamber to increase the viscosity of the material adjacent the open side and bottom, and rotating means engageable withthe material drawn from the chamber to attenuate the material into a filament of rectangular cross-section;

9. Apparatus for forming heat-softened mineral material into a filamentof rectangular cross-section includ-,

ing, in combination, arecepta'cle adapted to contain heat softened mineral material, a shield secured to and disposed beneath the receptacle, said shield defining a chamber having an open side and an open bottom region, means for conveying material from the supply into the shield, said open side and bottom providing direct contact of ambient air with the exposed area of the material in the chamber to increase the viscosity of the material adjacent the open side and bottom, means engageable with material drawn from the chamber to attenuate the material of difi'erential viscosities to a filament, and a coating device disposed adjacent the shield of noncircular cross-section for applying a layer of metal onto the filament at the region of attenuation.

10. Apparatus for forming heat-softened material into a filament of noncircular cross-section including, in combination, a feeder adapted to contain heat-softened material, a shield secured to the feeder, said shield being formed with Walls arranged to provide a laterm open side, orifice means for flowing heat-softened material from the feeder into the region defined by the shield for maintaining a quantity of the material in said region, and means for drawing material from the region defined by the shield into a filament of noncircular cross-section.

11. Apparatus for forming heat-softened material into a filament of noncircular cross-section including, in combination, a feeder adapted to contain heat-softened material, a shield depending from the feeder, said shield being formed with spaced side walls and a wall connecting the side walls providing a lateral open area, orifice means for flowing heat-softened material from the feeder into the region defined by the shield whereby a quantity of the material is suspended in said region, and means for drawing material from the region defined by the shield into a filament of noncircular cross-section, means containing flowable metal disposed adjacent the path of the filament, said filament being moved into contact with the metal at the region of attenuation of the filament whereby a coating of the metal is applied to the filament.

12. Apparatus for forming heat-softened material into i a filament of noncircular cross-section including,- in combinatior'i, a feeder adapted to contain heat-softened material, a shield secured to' and depending from the feeder, said shield being formed with a rear wall andspaced side walls joined to the rear wall defining a generally cubically shaped region having an open side and open bottom, means for flowing material from the feeder into the region to maintain a quantity of the material suspended in said region, the surface of the material in the chamber exposed to the surrounding 7 air being cooled thereby and its viscosity increased, means for attenuating a linear body from the material in the chamber at a zone of convergence of material of different viscosities to form a filament, said attenuating means includinga rotatable member engageable with the filament for advancing the same.

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